1. Field of the Invention
The present invention pertains to dishwasher pumps and, more particularly, to a dishwasher pump and wash liquid filtration system.
2. Description of the Prior Art
As dishwashing machines have developed, it has become desirable to combine and coordinate wash water pumping and filtration operations. Filtration devices are typically integrally provided in the pump housing, or provided in spaced relation to the housing and fluidly connected thereto.
U.S. Pat. Nos. 4,319,598 and 4,319,599, which issued to Dingler et al. on Mar. 16, 1982, are exemplary of reversible, dual impeller pumps which include a soil separation or collection circuit. In the wash mode, the drain impeller is inoperative and the wash impeller takes wash liquid from the dishwasher sump, pumping a majority of the liquid back into the dishwasher tub through the wash arms. A centrifugally sampled portion of the wash liquid is diverted via an annular guide chamber and a small opening into a sealed accumulator chamber in which heavy soil separates or settles by gravity. A stand pipe extending from the bottom of the accumulator chamber permits surface liquid within the accumulator to return to the pump inlet, thereby recirculating cleansed liquid within the dishwasher. When the motor is reversed, the pump is operated in the drain or pump-out mode. The wash impeller is generally inoperable and the drain impeller pumps wash liquid from the sump to drain.
Another reversibly-operated dual impeller pump is disclosed in U.S. Pat. No. 4,612,947, which issued to Duncan on Sep. 23, 1986. In the '947 patent, during wash mode, an upper impeller supplies wash liquid to the lower or main wash arm and a lower impeller supplies wash liquid to auxiliary spray arms and to a separation or settling chamber. A majority of the water pumped by the lower impeller is directed toward the auxiliary wash arms, with a relatively smaller portion going to the settling chamber. Wash liquid, less the settled soil, exits the settling chamber and returns to the dishwasher cavity via a hole in a separation chamber top. In a second embodiment of the pump, the separation chamber top does not provide a hole, and the wash liquid is instead re-introduced into the lower impeller chamber and mixed with other liquid and thereafter distributed to the auxiliary spray arms or the settling chamber. When operated in the drain or pump-out mode the upper impeller is generally inoperable and the lower impeller pumps Wash liquid from the sump to drain. The Dingler and Duncan patents described above rely solely upon settling to filter or remove solid particles from the wash liquid.
U.S. Pat. No. 4,392,891 which issued to Meyers on Jul. 12, 1983, discloses another reversible, dual impeller pump having a soil collection circuit. However, unlike the Duncan and Dingler pumps disclosed hereinbefore, in the Meyers' pump the soil collection circuit is completely independent of the primary spray means. During wash mode, the upper impeller supplies wash liquid to the wash arms while the lower impeller supplies wash liquid to the soil collection circuit. The soil collector includes a mesh filter for filtering food soil from fluid passing therethrough and holds or retains the soil for discharge during draining of the machine. For references which show related pump and filtration schemes see U.S. Pat. Nos. 4,448,359; 4,559,959; and 4,673,441 which issued to Meyers on May 15, 1984; Dec. 24, 1985; and Jun. 16, 1987, respectively.
U.S. Pat. No. 5,165,433, which issued to Meyers on Nov. 24, 1992, discloses another combination pump and filter. The '433 patent is directed toward a dual impeller centrifugal pump wherein a portion of the water pumped by an upper impeller is sampled, directed toward an intermediate guide chamber and thereafter introduced into a soil collecting chamber via a hole. Heavy soil settles in the collecting chamber, while floating soil is filtered by a mesh filter screen. Cleansed liquid is re-introduced into the dishwasher sump and thereafter re-pumped by the upper impeller. Although there are two impellers in the '433 patent, the lower impeller is generally inoperable during the wash cycle and does not supply liquid to either the wash arm or the collecting chamber. Upon study of the references, it will be apparent that the pump described in the '433 patent is a combination of the pumps disclosed in the above-described U.S. Pat. Nos. 4,392,891 and 4,319,599.
U.S. Pat. Nos. 4,346,723 and 4,468,333, which issued to Geiger on Aug. 31, 1982 and Aug. 28, 1984, respectively, disclose yet another dual impeller, reversibly operated pump. The pumps disclosed in the Geiger patents have a soil collector circuit which is supplied with wash liquid from the drain impeller. The soil collector circuit includes a cylindrically-shaped mesh filter which is adapted and arranged to remove soil from wash liquid passing therethrough during a wash or recirculation mode. Wash liquid reverses direction when the pump is operated in a drain mode, allowing the filtered soil to be conveyed therewith to drain.